#include<bits/stdc++.h>
using namespace std;
using ll = long long;

int main(){
    int n;
    cin>>n;
    vector<ll> a(n);
    for(int i = 0;i<n;i++) cin>>a[i];
    vector<ll> dp(1<<n,0);
    for(int i = 0;i<1<<n;i++){
        for(int j = 0;j<n;j++) {
            if(i>>j&1) continue;
            for(int k = j + 1;k<n;k++) {
                if(i>>k&1) continue;
                assert(j!=k);
                int nxt = i | 1<<j | 1<<k;
                dp[nxt] = max(dp[nxt],dp[i]+(ll)a[j]^a[k]);
            }
        }
    }
    cout<<dp[(int)(1<<n)-1]<<endl;
    //for(int i = 0;i<1<<n;i++) cout<<dp[i]<<" ";
}